CN108516548A - A kind of preparation method of high mesoporous rate activated carbon and its activated carbon of acquisition - Google Patents

Abstract

The invention discloses a method for preparing high-mesopority biomass activated carbon and the obtained activated carbon. The method includes the steps of raw material crushing, acid hydrothermal carbonization, low-temperature activation, high-temperature activation, and water washing. Phosphoric acid is used as an activator. Biomass is prepared into activated carbon. Compared with the prior art, the present invention has the following advantages: hydrothermal carbonization and primary air activation are used to promote the hydrolysis and dehydration reaction of phosphoric acid on high polysaccharides such as cellulose and hemicellulose in biomass, and reduce the condensation reaction between phosphoric acids. The activation of phosphoric acid is promoted; the production process is simple and the equipment requirements are low; no need to add other catalysts, which reduces the production cost; the phosphoric acid used for activation can be recycled after washing with water, and has no pollution; the prepared activated carbon has a large specific surface area and developed Pore structure, in which the total pore volume is 2.0447cm ³ ·g ^‑1 , the mesopore volume is 1.976cm ³ ·g ^‑1 , and the mesoporosity reaches over 95%. It has a good removal effect on methylene blue and has a great market application prospects.

Description

A kind of preparation method of high mesopority activated carbon and the activated carbon obtained therefrom

technical field

The present invention designs the technical field of activated carbon preparation, and in particular relates to a preparation method of high mesoporous activated carbon and the obtained activated carbon.

Background technique

Activated carbon has a wide range of applications in the industrial field. Due to its developed pore structure and high specific surface area, it has a wide range of applications in gas adsorption, liquid phase decolorization, environmental protection, catalyst carrier and electrode materials. For ordinary activated carbon, most of the pores are micropores with a diameter less than 2nm, and some dye molecules or gas molecules with larger molecules cannot enter the pores, resulting in a decrease in the adsorption capacity of activated carbon. Therefore, ordinary activated carbons have very limited applications in the adsorption of macromolecular pollutants.

Compared with ordinary activated carbon, mesoporous activated carbon has broad application prospects in the fields of adsorption, separation and catalysis of macromolecular pollutants due to its good hydrophobicity, large pore volume, and good electrical conductivity.

At present, mesoporous activated carbon is mainly prepared by the template method, using nanocrystalline structure materials or mesoporous materials as templates, filling and growing carbon source materials in the pores, and obtaining a replica structure through in situ conversion. For example, Chinese patent document CN 105036250 A discloses a preparation method and application of an activated carbon fiber loaded ordered mesoporous carbon-graphene composite material, using graphite as a precursor to prepare a graphene oxide-activated carbon fiber composite material, and then using Phenolic resin is used as a precursor, F127 is used as a template, and the two are calcined at high temperature in proportion to obtain a new type of ordered mesoporous carbon material; Chinese patent document CN 104140090 A discloses a preparation method of a hydrophilic ordered mesoporous carbon material TSC-1 , which uses SBA-15 mesoporous molecular sieve as the master template, and carbonizes its internal P123 copolymer template at high temperature to generate ordered mesoporous carbon material TSC-1. Due to the high cost of raw materials, the large amount of water pollution in the preparation process, and the need to remove templates during the synthesis process, the above-mentioned template method has complicated processes, long production cycles, and heavy pollution in practical applications, and is not suitable for large-scale production. Production.

Chinese patent CN 103359729 A discloses a new method for the preparation of mesoporous activated carbon, which uses carbohydrates, wood or bamboo as the starting material, and uses acidic ionic liquid as the solvent and catalyst for ionic thermal carbonization, and then is activated by _CO2. Mesoporous activated carbon. Due to different surfactants, the structure of activated carbon can be rod-shaped, spherical and membrane-shaped. The ion thermal carbonization process has a low reaction temperature and does not need to be pressurized. However, this process needs to add water and ethanol to wash alternately after ion thermal carbonization, which is more polluting and time-consuming; the specific surface area of the prepared activated carbon is low, only 289-469m ² /g.

Therefore, looking for a process of mesoporous activated carbon with environmental friendliness, high yield, simple process and well-developed pore structure has become a research hotspot.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a preparation method of activated carbon with high mesopority.

The present invention is achieved through the following technical solutions: a preparation method of high mesoporous activated carbon, characterized in that the steps are as follows:

Step 1, raw material crushing, using sawdust as raw material, and further crushing it;

Step 2, acid hydrothermal carbonization, mixing the sawdust pulverized in step 1 with phosphoric acid solution, and heating in a sealed environment;

Step 3, low-temperature activation, directly heat and activate the solid-liquid mixture obtained in Step 2 at 200°C under an air atmosphere;

Step 4, high temperature activation, under a nitrogen atmosphere, heat and activate the powder obtained in step 3 at 300-500°C;

Step 5, washing and drying, the product obtained in step 4 is washed with water until the raffinate is neutral, and then dried to obtain the high mesopority activated carbon.

As a further improvement to the above scheme, the phosphoric acid solution used in the second step is a phosphoric acid solution with a mass fraction of 41% to 62%.

As a further improvement to the above scheme, the mass ratio of phosphoric acid solution to sawdust in step 2 is 1:4.

As a further improvement to the above scheme, the specific step of heating in a sealed environment in step 2 is to seal the reaction kettle containing the mixture of sawdust and phosphoric acid solution, place it in an oven and heat it to 200°C, and keep it warm for 6 hours.

As a further improvement to the above scheme, the activation time in step 3 is 6 h, heating is carried out in a tube furnace, and the air flow rate in the tube furnace is 0.5 mL·min ^-1 .

As a further improvement to the above scheme, the activation time in step 4 is 60 min, heating in a tube furnace, nitrogen in the tube furnace is used as a protective gas, and the nitrogen flow rate is 0.5 mL·min ^-1 .

As a further improvement to the above-mentioned scheme, in the water washing process in step five, the product of step four is first heated to a boiling state in deionized water and kept for 30s, then rinsed with deionized water until the raffinate is neutral and then dried to obtain the high Mesoporous activated carbon.

As a further improvement to the above scheme, the sawdust is crushed to 40-80 mesh.

The present invention also provides a high mesopority activated carbon, characterized in that: the high mesopority activated carbon is obtained by using any one of the above high mesopority activated carbon preparation methods.

Compared with the prior art, the present invention has the following advantages: this scheme adopts a three-step activation method, first heat-treating the biomass with acid water, then using air for low-temperature activation, and finally activating under inert gas, the production process is simple, and the equipment requirements are low; no need to add Other catalysts reduce the production cost; the phosphoric acid used for activation can be recycled after washing with water, and has no pollution; it overcomes the defects of complex process, long production cycle and large pollution of the template method; the BET specific surface area of the prepared high mesoporous activated carbon can reach 2400m ² ·g ^-1 , the total pore volume is 2.0447cm ³ ·g ^-1 , the mesopore volume is 1.976cm ³ ·g ^-1 , the mesoporosity reaches over 95%, and the methylene blue adsorption value is 611.26mg·g ^{- 1.} It has a well-developed pore structure and excellent adsorption capacity; it has great market application prospects.

Description of drawings

Fig. 1 is the 10000 times scanning electron micrograph of the high mesopority biomass activated carbon obtained in the present invention.

Fig. 2 is a 60,000 times scanning electron micrograph of the high mesopority biomass activated carbon obtained in the present invention.

Fig. 3 is a 120,000 times scanning electron micrograph of the high mesopority biomass activated carbon obtained in the present invention.

Fig. 4 is the nitrogen adsorption and desorption curve diagram of the high mesopority biomass activated carbon obtained in the present invention.

Detailed ways

The embodiments of the present invention are described in detail below. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided, but the protection scope of the present invention is not limited to the following implementation example.

Example 1

A kind of preparation method of high mesopority activated carbon is characterized in that comprising the following steps:

Step 1, raw material crushing, the recycled wood sawdust is crushed to 40-80 mesh, so as to ensure the consistency of raw material particle size.

Step 2, acid hydrothermal carbonization, take 4g of the biomass particles obtained in step 1 and place them in a reaction kettle with a 50mL Teflon liner, add 30mL of phosphoric acid solution with a mass fraction of 41%, and stir fully. At this time, phosphoric acid and sawdust The mass ratio of the reactor is 1:4. After sealing the reactor, place it in an oven and heat it to 200°C for 6 hours. Phosphoric acid is a medium-strength protonic acid, which can significantly promote the hydrolysis of high polysaccharides such as cellulose to form oligosaccharides or monosaccharide products, and then penetrate into the interior of the biomass structure to produce activation, and phosphoric acid can catalyze high polysaccharides and their Dehydration of the product. During the hydrothermal reaction, the pressure of the water vapor inside the reactor reaches 15Mpa, which can promote the hydrolysis and dehydration of the high polysaccharides in the biomass, so that phosphoric acid can enter the biomass, improving the performance and output of activated carbon, and the reaction kettle Water vapor can make more phosphoric acid exist in the form of protonic acid, which reduces the condensation reaction between phosphoric acid molecules and reduces the amount of phosphoric acid required for activation.

Step 3, one-time activation, place the product obtained in step 2 in a tube furnace, and activate by heating, the activation temperature is 200°C, and the activation time is 6h. Air is ventilated in the tube furnace, and the air velocity is controlled to be 0.5mL·min ^-1 . Air activation increases the oxygen-containing functional groups of activated carbons.

Step 4, secondary activation, the product obtained in step 3 is placed in a tube furnace, and activated by heating, the activation temperature is 450°C, and the activation time is 60 minutes. Nitrogen is passed through the tube furnace as a protective gas, and the rate of nitrogen is controlled at 0.5mL·min ^-1 . During the secondary activation, the hydroxyl group of the phosphoric acid molecule undergoes a cross-linking reaction with the carboxyl group in the polysaccharide and its degradation products, and condenses into a phosphate bond. The reaction formula is as follows:

Cell-OH+H ₃ PO ₄ fCell-OH ₂ PO ₃ +H ₂ O

Step 5: washing and drying with water, placing the activated carbon obtained in step 4 in deionized water, heating to a boiling state and keeping it for 30 seconds, then washing with deionized water until the raffinate is neutral, then drying to obtain the high mesopority activated carbon. After the complex carbide formed by phosphoric acid and biomass polymer is washed off, the gaps left become the pores of activated carbon.

During the acid hydrothermal process, phosphoric acid can enter the interior of biomass, which promotes the hydrolysis of high polysaccharides in biomass by phosphoric acid, and reduces the condensation reaction between phosphoric acid molecules. At this time, phosphoric acid and biomass polymers have a slight interaction Condensation reaction mainly produces micropores. When phosphoric acid is activated in the air, the oxygen in the air will slowly oxidize the cellulose and hemicellulose in the biomass that are not combined with phosphoric acid molecules, making the pore size further increase. Activated in inert gas At this time, the cross-linking effect between phosphoric acid and biomass molecules is enhanced, and a large number of phosphate bonds are formed, which prevents the thermal contraction of the cell wall. In the water washing step, the complex carbide formed by phosphoric acid and biomass polymer is washed away, and the space occupied by it forms abundant mesopores.

The production cost of phosphoric acid is low, and the product itself is non-toxic. Compared with traditional alkaline activators and alkali metal salt activators, the temperature required for activation is lower, energy consumption is lower, and it is safer. Therefore, phosphoric acid is used to prepare biomass-based activated carbon. wider range.

Example 2

A kind of preparation method of high mesopority activated carbon is characterized in that comprising the following steps:

Step 1, raw material crushing, the recycled wood sawdust is crushed to 40-80 mesh, so as to ensure the consistency of raw material particle size.

Step 2, acid hydrothermal carbonization, take 4g of biomass particles obtained in step 1 and place them in a reaction kettle with a 50mL Teflon liner, add 30mL of phosphoric acid solution with a mass fraction of 49%, and stir fully. At this time, phosphoric acid and sawdust The mass ratio of the reactor is 1:5. After sealing the reactor, place it in an oven and heat it to 200°C for 9 hours. Phosphoric acid is a medium-strength protonic acid, which can significantly promote the hydrolysis of high polysaccharides such as cellulose to form oligosaccharides or monosaccharide products, and then penetrate into the interior of the biomass structure to produce activation, and phosphoric acid can catalyze high polysaccharides and their Dehydration of the product. During the hydrothermal reaction, the pressure of the water vapor inside the reactor reaches 15Mpa, which can promote the hydrolysis and dehydration of the high polysaccharides in the biomass, so that phosphoric acid can enter the biomass, improving the performance and output of activated carbon, and the reaction kettle Water vapor can make more phosphoric acid exist in the form of protonic acid, which reduces the condensation reaction between phosphoric acid molecules and reduces the amount of phosphoric acid required for activation.

Step 3, one-time activation, place the product obtained in step 2 in a tube furnace, and activate by heating, the activation temperature is 200°C, and the activation time is 3h. Air is ventilated in the tube furnace, and the air rate is controlled to be 0.5mL·min ^-1 . Air activation increases the oxygen-containing functional groups of activated carbons.

Step 4, secondary activation, the product obtained in step 3 is placed in a tube furnace, and activated by heating, the activation temperature is 450°C, and the activation time is 90 minutes. Nitrogen is passed through the tube furnace as a protective gas, and the rate of nitrogen is controlled at 0.5mL·min ^-1 . During the secondary activation, the hydroxyl group of the phosphoric acid molecule undergoes a cross-linking reaction with the carboxyl group in the high polysaccharide and its decomposed product, and condenses into a phosphate bond. The reaction formula is as follows:

Cell-OH+H ₃ PO ₄ fCell-OH ₂ PO ₃ +H ₂ O

Step 5, washing and drying, place the activated carbon obtained in step 4 in deionized water, heat to boiling state and keep for 30s, then rinse with deionized water until the raffinate is neutral, then dry to obtain the high mesoporous biomass Activated carbon. After the complex carbide formed by phosphoric acid and biomass polymers in step 4 is washed off, the remaining voids become the pores of activated carbon.

During the acid hydrothermal process, phosphoric acid can enter the interior of biomass, which promotes the hydrolysis of high polysaccharides in biomass by phosphoric acid, and reduces the condensation reaction between phosphoric acid molecules. At this time, phosphoric acid and biomass polymers have a slight interaction Condensation reaction mainly produces micropores. When phosphoric acid is activated in the air, the oxygen in the air will slowly oxidize the cellulose and hemicellulose in the biomass that are not combined with phosphoric acid molecules, making the pore size further increase. Activated in inert gas At this time, the cross-linking effect between phosphoric acid and biomass molecules is enhanced, and a large number of phosphate bonds are formed, which prevents the thermal contraction of the cell wall. In the water washing step, the complex carbide formed by phosphoric acid and biomass polymer is washed away, and the space occupied by it forms abundant mesopores.

The production cost of phosphoric acid is low, and the product itself is non-toxic. Compared with traditional alkaline activators and alkali metal salt activators, the temperature required for activation is lower, energy consumption is lower, and it is safer. Therefore, phosphoric acid is used to prepare biomass-based activated carbon. wider range.

Example 3

A preparation method of high mesopority biomass activated carbon is characterized in that comprising the following steps:

Step 1, raw material crushing, the recycled wood sawdust is crushed to 40-80 mesh, so as to ensure the consistency of raw material particle size.

Step 2, acid hydrothermal carbonization, take 4g of the biomass particles obtained in step 1 and place them in a reaction kettle with a 50mL Teflon liner, add 30mL of phosphoric acid solution with a mass fraction of 62%, and stir fully. The mass ratio of the substances is 1:7. After sealing the reactor, place it in an oven and heat it to 200°C for 12 hours. Phosphoric acid is a medium-strength protonic acid, which can significantly promote the hydrolysis of high polysaccharides such as cellulose to form oligosaccharides or monosaccharide products, and then penetrate into the interior of the biomass structure to produce activation, and phosphoric acid can catalyze high polysaccharides and their Dehydration of the product. During the hydrothermal reaction, the pressure of the water vapor inside the reactor reaches 15Mpa, which can promote the hydrolysis and dehydration of the high polysaccharides in the biomass, so that phosphoric acid can enter the biomass, improving the performance and output of activated carbon, and the reaction kettle Water vapor can make more phosphoric acid exist in the form of protonic acid, which reduces the condensation reaction between phosphoric acid molecules and reduces the amount of phosphoric acid required for activation.

Step 3, one-time activation, place the product obtained in step 2 in a tube furnace, and activate by heating, the activation temperature is 200°C, and the activation time is 3h. Air is ventilated in the tube furnace, and the air rate is controlled to be 0.5mL·min ^-1 . Air activation increases the oxygen-containing functional groups of activated carbons.

Step 4, secondary activation, the product obtained in step 3 is placed in a tube furnace, and activated by heating, the activation temperature is 400°C, and the activation time is 60 minutes. Nitrogen is passed through the tube furnace as a protective gas, and the rate of nitrogen is controlled at 0.5mL·min ^-1 . During the secondary activation, the hydroxyl group of the phosphoric acid molecule undergoes a cross-linking reaction with the carboxyl group in the high polysaccharide and its decomposed product, and condenses into a phosphate bond. The reaction formula is as follows:

Cell-OH+H ₃ PO ₄ fCell-OH ₂ PO ₃ +H ₂ O

Step 5, washing and drying, place the activated carbon obtained in step 4 in deionized water, heat to boiling state and keep for 30s, then rinse with deionized water until the raffinate is neutral, then dry to obtain the high mesoporous biomass Activated carbon. After the complex carbide formed by phosphoric acid and biomass polymers in step 4 is washed off, the remaining voids become the pores of activated carbon.

During the acid hydrothermal process, phosphoric acid can enter the interior of biomass, which promotes the hydrolysis of high polysaccharides in biomass by phosphoric acid, and reduces the condensation reaction between phosphoric acid molecules. At this time, phosphoric acid and biomass polymers have a slight interaction Condensation reaction mainly produces micropores. When phosphoric acid is activated in the air, the oxygen in the air will slowly oxidize the cellulose and hemicellulose in the biomass that are not combined with phosphoric acid molecules, making the pore size further increase. Activated in inert gas At this time, the cross-linking effect between phosphoric acid and biomass molecules is enhanced, and a large number of phosphate bonds are formed, which prevents the thermal contraction of the cell wall. In the water washing step, the complex carbide formed by phosphoric acid and biomass polymer is washed away, and the space occupied by it forms abundant mesopores.

The production cost of phosphoric acid is low, and the product itself is non-toxic. Compared with traditional alkaline activators and alkali metal salt activators, the temperature required for activation is lower, energy consumption is lower, and it is safer. Therefore, phosphoric acid is used to prepare biomass-based activated carbon. wider range.

Example 4

A preparation method of high mesopority biomass activated carbon is characterized in that comprising the following steps:

Step 1, raw material crushing, the recycled wood sawdust is crushed to 40-80 mesh, so as to ensure the consistency of raw material particle size.

Step 2, acid hydrothermal carbonization, take 4g of the biomass particles obtained in step 1 and place them in a reaction kettle with a 50mL Teflon liner, add 30mL of phosphoric acid solution with a mass fraction of 62%, and stir fully. The mass ratio of the substances is 1:7. After sealing the reactor, place it in an oven and heat it to 200°C for 12 hours. Phosphoric acid is a medium-strength protonic acid, which can significantly promote the hydrolysis of high polysaccharides such as cellulose to form oligosaccharides or monosaccharide products, and then penetrate into the interior of the biomass structure to produce activation, and phosphoric acid can catalyze high polysaccharides and their Dehydration of the product. During the hydrothermal reaction, the pressure of the water vapor inside the reactor reaches 15Mpa, which can promote the hydrolysis and dehydration of the high polysaccharides in the biomass, so that phosphoric acid can enter the biomass, improving the performance and output of activated carbon, and the reaction kettle Water vapor can make more phosphoric acid exist in the form of protonic acid, which reduces the condensation reaction between phosphoric acid molecules and reduces the amount of phosphoric acid required for activation.

Step 3, one-time activation, place the product obtained in step 2 in a tube furnace, and activate by heating, the activation temperature is 200°C, and the activation time is 3h. Air is ventilated in the tube furnace, and the air velocity is controlled to be 0.5mL·min ^-1 . Air activation increases the oxygen-containing functional groups of activated carbons.

Step 4, secondary activation, the product obtained in step 3 is placed in a tube furnace, and activated by heating, the activation temperature is 500°C, and the activation time is 60 minutes. Nitrogen is passed through the tube furnace as a protective gas, and the rate of nitrogen is controlled at 0.5mL·min ^-1 . During the secondary activation, the hydroxyl group of the phosphoric acid molecule undergoes a cross-linking reaction with the carboxyl group in the high polysaccharide and its decomposed product, and condenses into a phosphate bond. The reaction formula is as follows:

Cell-OH+H ₃ PO ₄ fCell-OH ₂ PO ₃ +H ₂ O

Step 5, washing and drying, place the activated carbon obtained in step 4 in deionized water, heat to boiling state and keep for 30s, then rinse with deionized water until the raffinate is neutral, then dry to obtain the high mesoporous biomass Activated carbon. After the complex carbide formed by phosphoric acid and biomass polymers in step 4 is washed off, the remaining voids become the pores of activated carbon.

During the acid hydrothermal process, phosphoric acid can enter the interior of biomass, which promotes the hydrolysis of high polysaccharides in biomass by phosphoric acid, and reduces the condensation reaction between phosphoric acid molecules. At this time, phosphoric acid and biomass polymers have a slight interaction Condensation reaction mainly produces micropores. When phosphoric acid is activated in the air, the oxygen in the air will slowly oxidize the cellulose and hemicellulose in the biomass that are not combined with phosphoric acid molecules, making the pore size further increase. Activated in inert gas At this time, the cross-linking effect between phosphoric acid and biomass molecules is enhanced, and a large number of phosphate bonds are formed, which prevents the thermal contraction of the cell wall. In the water washing step, the complex carbide formed by phosphoric acid and biomass polymer is washed away, and the space occupied by it forms abundant mesopores.

The production cost of phosphoric acid is low, and the product itself is non-toxic. Compared with traditional alkaline activators and alkali metal salt activators, the temperature required for activation is lower, energy consumption is lower, and it is safer. Therefore, phosphoric acid is used to prepare biomass-based activated carbon. wider range.

Example 4

A preparation method of high mesopority biomass activated carbon is characterized in that comprising the following steps:

Step 1, raw material crushing, the recycled wood sawdust is crushed to 40-80 mesh, so as to ensure the consistency of raw material particle size.

Step 2, acid hydrothermal carbonization, take 4g of the biomass particles obtained in step 1 and place them in a reaction kettle with a 50mL Teflon liner, add 30mL of phosphoric acid solution with a mass fraction of 62%, and stir fully. The mass ratio of the substances is 1:7. After sealing the reactor, place it in an oven and heat it to 200°C for 12 hours. Phosphoric acid is a medium-strength protonic acid, which can significantly promote the hydrolysis of high polysaccharides such as cellulose to form oligosaccharides or monosaccharide products, and then penetrate into the interior of the biomass structure to produce activation, and phosphoric acid can catalyze high polysaccharides and their Dehydration of the product. During the hydrothermal reaction, the pressure of the water vapor inside the reactor reaches 15Mpa, which can promote the hydrolysis and dehydration of the high polysaccharides in the biomass, so that phosphoric acid can enter the biomass, improving the performance and output of activated carbon, and the reaction kettle Water vapor can make more phosphoric acid exist in the form of protonic acid, which reduces the condensation reaction between phosphoric acid molecules and reduces the amount of phosphoric acid required for activation.

Step 3, one-time activation, place the product obtained in step 2 in a tube furnace, and activate by heating, the activation temperature is 200°C, and the activation time is 3h. Air is ventilated in the tube furnace, and the air velocity is controlled to be 0.5mL·min ^-1 . Air activation increases the oxygen-containing functional groups of activated carbons.

Step 4, secondary activation, the product obtained in step 3 is placed in a tube furnace, and activated by heating, the activation temperature is 300°C, and the activation time is 60 minutes. Nitrogen is passed through the tube furnace as a protective gas, and the rate of nitrogen is controlled at 0.5mL·min ^-1 . During the secondary activation, the hydroxyl group of the phosphoric acid molecule undergoes a cross-linking reaction with the carboxyl group in the high polysaccharide and its decomposed product, and condenses into a phosphate bond. The reaction formula is as follows:

Cell-OH+H ₃ PO ₄ fCell-OH ₂ PO ₃ +H ₂ O

Step 5, washing and drying, place the activated carbon obtained in step 4 in deionized water, heat to boiling state and keep for 30s, then rinse with deionized water until the raffinate is neutral, then dry to obtain the high mesoporous biomass Activated carbon. After the complex carbide formed by phosphoric acid and biomass polymers in step 4 is washed off, the remaining voids become the pores of activated carbon.

During the acid hydrothermal process, phosphoric acid can enter the interior of biomass, which promotes the hydrolysis of high polysaccharides in biomass by phosphoric acid, and reduces the condensation reaction between phosphoric acid molecules. At this time, phosphoric acid and biomass polymers have a slight interaction Condensation reaction mainly produces micropores. When phosphoric acid is activated in the air, the oxygen in the air will slowly oxidize the cellulose and hemicellulose in the biomass that are not combined with phosphoric acid molecules, making the pore size further increase. Activated in inert gas At this time, the cross-linking effect between phosphoric acid and biomass molecules is enhanced, and a large number of phosphate bonds are formed, which prevents the thermal contraction of the cell wall. In the water washing step, the complex carbide formed by phosphoric acid and biomass polymer is washed away, and the space occupied by it forms abundant mesopores.

The production cost of phosphoric acid is low, and the product itself is non-toxic. Compared with traditional alkaline activators and alkali metal salt activators, the temperature required for activation is lower, energy consumption is lower, and it is safer. Therefore, phosphoric acid is used to prepare biomass-based activated carbon. wider range.

Example 6

A kind of high mesopority biomass activated carbon, described high mesopority biomass activated carbon is obtained by the preparation method of high mesopority biomass activated carbon described in embodiment 1, 2, 3, 4 and 5.

After testing, the BET specific surface area of the activated carbon obtained in Example 1 is 2433.82m ² ·g ^-1 , the total pore volume is 2.0447cm ³ ·g ^-1 , the mesopore volume is 1.976cm 3 ·g ^-1 , and the mesopore volume is 1.976cm ³ ·g -1 . 96.64%, the average pore size is 3.0237nm; its methylene blue adsorption value is 611.26mg/g, which is 4.7 times of the national first-class product standard in GB/T 13803.2-1999 "Activated Carbon for Wooden Water Purification": 130mg.g ^-1 , proving that activated carbon has excellent removal ability for methylene blue.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (9)

1. a kind of preparation method of high mesoporous rate activated carbon, it is characterised in that steps are as follows：

Step 1: raw material crushes, using sawdust as raw material, and it is further crushed；

Step 2: sour water heat carbonizes, the sawdust that step 1 crushes is mixed with phosphoric acid solution, and heats in a sealed meter environment；

Step 3: low-temperature activation, under air atmosphere, directly the solidliquid mixture that step 2 obtains is heated at 200 DEG C Activation；

Step 4: high-temperature activation, under nitrogen atmosphere, the powder that step 3 obtains is subjected to heat-activated at 300~500 DEG C；

Step 5: washing drying, the product that step 4 obtains is carried out being washed to raffinate being dry after neutrality, you can described in acquisition High mesoporous rate activated carbon.

2. a kind of preparation method of high mesoporous rate activated carbon as described in claim 1, it is characterised in that：The phosphorus used in step 2 Acid solution is the phosphoric acid solution that mass fraction is 41%~62%.

3. a kind of preparation method of high mesoporous rate activated carbon as described in claim 1, it is characterised in that：Phosphoric acid solution in step 2 Mass ratio with sawdust is 1:4~1:7.

4. a kind of preparation method of high mesoporous rate activated carbon as described in claim 1, it is characterised in that：In sealing ring in step 2 Heated in border the specific steps are will be loaded with to place baking oven after the sealing of sawdust and phosphoric acid solution mixture reaction kettle and be heated to 200 DEG C, keep the temperature 6h.

5. a kind of preparation method of high mesoporous rate activated carbon as described in claim 1, it is characterised in that：Soak time in step 3 It for 6h, is heated in tube furnace, air flow rate is 0.5mLmin in tube furnace^-1。

6. a kind of preparation method of high mesoporous rate activated carbon as described in claim 1, it is characterised in that：Soak time in step 4 It for 60min, is heated in tube furnace, it is protective gas that nitrogen is led in tube furnace, and nitrogen flow rate is 0.5mLmin^-1。

7. a kind of preparation method of high mesoporous rate activated carbon as described in claim 1, it is characterised in that：Water-washing process in step 5 It is middle that the product of step 4 is first heated to fluidized state in deionized water and keeps 30s, then rinsed to raffinate with deionized water The mesoporous rate activated carbon of height is obtained to be dry after neutrality.

8. a kind of preparation method of high mesoporous rate activated carbon as described in claim 1, it is characterised in that：Sawdust is crushed to 40-80 Mesh.

9. a kind of high mesoporous rate activated carbon, it is characterised in that：The mesoporous rate activated carbon of height is appointed using in claim 1 to 8 What a kind of preparation method of high mesoporous rate activated carbon obtained.